Real Time Signal Processing And Optimal Control Technology On Adaptive Optics Systems

The adaptive optical systems(AOS)can detect and compenstate the wavefront aberrations due to the atmospheric turbulence and the optical systems,and are widely used in the high resolution imaging,high energy laser transmission and so on.As the core of the adpative optics systems,the wavefront control systems play an important role in the performance of the AOS.The paper mainly studies the real time,accuracy,and stability of the wavefront control system.First,the basic requirements are put forward according to the characteristics of the real time signal processing system.The compution loads are analyzed,and the bus architectures are structured,and the method based pipeline in time and parallel in space are proposed,and the platform using double DSPs and FPGA is studied.The experimental results show the platform can satisfy the real time and reliability,and the platform has been applied in several AOS.Second,the accuracy of gravity algorithm is sensitive to the noise in Shack-Hartmann wavefront sensor,which varies with temporality and spatiality rapidly.A method based on weighted function of the mean value and direction of local gradient in the moving windows is presented according to the characteristics of the Gaussian spot and noise distributing,and the theory and parameters determination of the method is analyzed.To investigate the effect of the optimum threshold estimation with the different spot size,spot strength and noise level,the proposed algorithm is compared with traditional methods.The simulation and experimental results show that the proposed method could achieve more accuracy estimation threshold,and the error between threshold using the method presented in the paper and theoretical optimum threshold is less than the traditional methods.And then,according to the influence of broadband and narrowband disturbance,which caused seperately by transmision medium and optics platform,the traditional laser beam stability systems is analyzed,and a method using two fast steering mirrors in series is presented in order to reduce the laser beam jitter,in which the first beam stability systems aimed to the narrowband disturbance and the second system resolved the broadband disturbance.So the both disturbances can be restrained at the same time.The residual errors are compared between the proposed method and classic control algorithm.The simulation and experimental results on laser beam stability verify the availability of the method.Finnaly,aimed at adaptive optics system using square geometry,and the waffle mode is an unsensed mode and there exists waffle voltage on the deformable mirror's drivers.The waffle voltage will accumulates and lead to the performance deterioration owing to the integral controller.A method using the penalty function on reconstruction voltage and projecting the controller voltage is proposed,and the couple between the Zernike mode and waffle is analyzed.Meanwhile,the method is verified in the real turbulence.The simulation and experimental results show the proposed method can restrain the waffle and improve the stability of system.